For all the uncertainty facing Ellis Johnson at a number of positions on defense, middle linebacker and outside (weakside) linebacker aren't two of them.

Shaq Wilson and Rodney Paulk have their physical limitations, but both players possess three important attributes Johnson craves in linebackers - football intelligence, experience and a knack for being in the right place at the right time.

If USC had a game scheduled for this week, Wilson would start at weakside (will) linebacker with Paulk lining up alongside him at middle (mike) linebacker for the opening snap.

Need proof? Check Saturday's scrimmage.

"The one thing I noticed is that when I have Shaq and Paulk out there, everything seems to be in gear," Johnson said following the scrimmage. "When they come off the field, we'll sometimes have a lot of mistakes."

Certainly, Paulk and Wilson have a huge advantage over their competitors in terms of experience, and that was evident again on Saturday. By the time Sept. 3 arrives, Johnson should be inclined to stick with experience because he knows what to expect from the veteran duo.

"If we had to play tomorrow, I'd put Rodney at mike and Shaq at will and then start rotating after that," Johnson said. "I also feel Shaq might be the best mike (linebacker). If we start getting more and more improvement at the will 'backer, maybe we'll have another combination. Today I started Rodney and Shaq the first eight plays and everything was glued together. (When we) started through the next rotation, I didn't see anything the linebackers did wrong but it wasn't nearly as quick and the operation wasn't as good. They're definitely more experienced and have had a real good camp."

Johnson pointed to USC's lack of tackling in preseason camp as a possible reason for the lack of crispness exhibited by some of the younger players.

"This is probably the second or third time we've tackled," Johnson said. "Obviously, we don't tackle very well. Only the great ones can do it once a week and be good at it. We never tackle enough. How much is enough? You can't get injuries. Before today, we had a little scrimmage for about 15 minutes and we had one inside drill. But some of them had never tackled a college running back, and that's where it shows up."

Johnson won't have to wait long for another opportunity to evaluate his players. USC is scheduled to scrimmage again on Tuesday at Williams-Brice Stadium.

Johnson is taking a cautious approach with Paulk and Wilson since both players are coming off injuries. Paulk has been bothered by balky knees the past couple of years, while Wilson is healthy again after missing most of last season with a severe hamstring pull. Johnson, though, is taking no chances.

"Rodney's knee is healed but he had a little soreness the other day so I cut his reps," Johnson said. "I don't think either one of them are going to play 60 or 70 snaps."

The battle for the backup spots at linebacker are still going on, though. Quin Smith and Damario Jeffery have been battling for the No. 2 spot at weakside linebacker, but Smith suffered a mild concussion in Saturday's scrimmage, so he will likely spend the next few days in a yellow jersey. Qua Gilchrist and Reginald Bowens are competing for the No. 2 middle linebacker job.

"I don't know how many reps (Smith) got before he had to come out. It's not very serious but they're very cautious about those now," Johnson said. "He only got about two series, less than 10 plays. That concerned me that I didn't get a good evaluation on him. Damario has had a pretty good camp and Toquavious (Gilchrist) has improved a lot, but he's a little bit behind those guys though."

Is the door open for freshman Cedrick Cooper to step inside? Maybe. But he still has a lot to learn.

"Coop's had a pretty good camp," Johnson said. "(But) he made two big mistakes right there at the end. It was threes versus threes on the last drive and he made two major mistakes and gave up a touchdown. He's still learning. Physically, he's going to be a really good football player. It's just going to take him a while to learn what he's doing."

In Johnson's view, the decision to stick with Wilson and Paulk at linebacker is stress-free compared to the safety spots. The free safety position has been troublesome since the spring, and who is going to back up D.J. Swearinger at strong safety?

Jimmy Legree's grip on the free safety spot strengthened after his biggest challenger, Brison Williams, suffered a broken lower arm that will sideline him for the season.

"It's a big hole," Johnson said. "We'll have to look at the film today and see if anyone maybe answered the bell and would be a possibility. He was really pushing Jimmy and both of them were making each other better. In fact, Brison was making some plays Jimmy can't make quite as consistently. That was a huge blow."

The severe injury forced Johnson to move some pieces around in the secondary. Redshirt freshman Sharrod Golightly had been competing mostly at strong safety behind Swearinger, but now he's double-training at both spots, and exited Saturday's scrimmage as the top backup at free safety.

Jadeveon Clowney? By his own admission, he's still learning the ropes about playing defensive end in the SEC, and has quickly discovered raw talent, however impressive, isn't enough. Technique and playing the assignment are critically important as well.

The defensive tackle spot next to Robertson remains up for grabs with the same quartet of challengers still battling it out for a spot in the rotation.

"Byron (Jerideau) has been having a good camp and Kelcy (Quarles) has been having a good camp and Aldrick (Fordham) has played very well," Johnson said. "If we had to pull the trigger right now, I'm not sure what Brad (Lawing) would say. I know they'd all probably play pretty equally, including Travian.

"He would get some rotation and reps with those guys. We're in pretty good shape. There are some young guys who are really getting better. J.T. (Surratt) has had a pretty good camp. He's made some strides and come a long way from where he was last year. The freshmen, it's tough on them in the interior. They've shown some good things and they're all getting better, too."

Phillip Dukes, arguably USC's top defensive tackle prospect in the 2011 signing class, has been hobbled by a high ankle sprain suffered earlier this week and will likely be sidelined for at least a couple of weeks.

"I don't know how serious that is," Johnson said. "I think it's just a sprain. But by the time he gets back ... If you're a freshman and miss two or three weeks, you're way behind. You may get back in the mix in six weeks but then we don't want to do it because we would want to get a redshirt for him if that happens. If he gets back in two or three days, he may get back in the hunt.

"It's going to be tough for any of those freshmen to unseat those four I told you about (Jerideau, Quarles, Fordham, Surratt). They're good football players, very experienced, and when they're out there, our linebackers play pretty well. When they're not out there, it's tough duty."

And then there's spur. Antonio Allen has already established himself as the starter with DeVonte Holloman behind him. But Holloman has been suspended for the Sept. 3 season opener because of his DUI arrest in June, leaving the defensive coaching staff to scramble to find a backup for that game.

Edward Muldrow would have been a candidate to fill the spot, but the true freshman is also suspended for the opener following his arrest in Five Points this summer for underage drinking.

Another true freshman, Kadetrix Marcus, was recently shifted to spur from safety and, understandably, showed his inexperience in Saturday's scrimmage.

"Antonio is playing pretty well," Johnson said. "DeVonte can not play the first game. Muldrow can't play the first game. We just moved Kadetrix Marcus two days ago and he lined up wrong about three times today and gave up some plays. He's a good player and if he learns how to line up, maybe that's his home and he can play there. He was one kid we thought could move in and play safety. We're in a bind right now. Do we put him back there and compete for the free safety or do we leave him at spur?"

Even cornerback hasn't been immune. Stephon Gilmore and Akeem Auguste (as long as he returns in time from his foot-arch injury) are the projected starters for the opening game, but the enigmatic Victor Hampton will sit the first three games due to academic issues dating back to the spring semester.

"We have all those kids being held out the first game," Johnson said. "With three DBs out, we have down-the-line problems. We have major considerations for that first game. We have to get 11 guys ready to roll. (East Carolina runs) a fast tempo and guys have to cover a bunch of kicks and punts too."